A new insight into the mechanism for cytosolic lipid droplet degradation in senescent leaves.

Leaf senescence involves lipid droplet (LD) degradation that produces toxic fatty acids, but little is known about how the toxic metabolites are isolated from the rest of the cellular components. Our ultramicroscopic characterization of cytosolic LD degradation in central vacuole-absent cells and central vacuole-containing cells of senescent watermelon leaves demonstrated two degradation pathways: the small vacuole-associated pathway and the central vacuole-associated pathway. This provided an insight into the subcellular mechanisms for the isolation of the fatty acids derived from LDs.

Function of terahertz spectra in monitoring the decomposing process of biological macromolecules and in investigating the causes of photoinhibition.

Chlorophyll a and β-carotene play an important role in harvesting light energy, which is used to drive photosynthesis in plants. In this study, terahertz (THz) and visible range spectra of chlorophyll a and β-carotene and their changes under light treatment were investigated. The results show that the all THz transmission and absorption spectra of chlorophyll a and β-carotene changed upon light treatment, with the maximum changes at 15 min of illumination indicating the greatest changes of the collective vibrational mode of chlorophyll a and β-carotene.

New methods for determining proton pumping ability and electron transfer activity of the cytochrome bc1 complex.

It is important to determine the electron transfer activity and proton pumping ability of the cytochrome bc1 complex for better understanding its structure and function. In this study, several methods for determining the electron transfer and proton pumping of the bc1 complex, including the traditional and the new methods, are presented and evaluated. For determining the proton pumping ability of the bc1 complex, the new stopped-flow method has a higher accuracy than the traditional pH meter method, and the new spectrophotometer method is more convenient than the traditional pH meter method.

Effect of mutations of arginine 94 on proton pumping, electron transfer, and superoxide anion generation in cytochrome b of the bc1 complex from Rhodobacter sphaeroides.

Proton transfer involving internal water molecules that provide hydrogen bonds and facilitate proton diffusion has been identified in some membrane proteins. Arg-94 in cytochrome b of the Rhodobacter sphaeroides bc(1) complex is fully conserved and is hydrogen-bonded to the heme propionate and a chain of water molecules. To further elucidate the role of Arg-94, we generated the mutations R94A, R94D, and R94N.

Thermal denaturation of CP43 studied by Fourier transform-infrared spectroscopy and terahertz time-domain spectroscopy.

Thermal denaturation of CP43 was studied by Fourier transform-infrared (FT-IR) spectroscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and terahertz time-domain spectroscopy (THz-TDS). Under heat treatment, the secondary structure of CP43 changed, and the main thermal transition occurred at 59 degrees C. During the process, CP43 aggregated at first, and then with increasing temperature degraded.

The guanidine hydrochloride-induced denaturation of CP43 and CP47 studied by terahertz time-domain spectroscopy.

Terahertz time-domain spectroscopy (THz-TDS) is a new technique in studying the conformational state of a molecule in recent years. In this work, we reported the first use of THz-TDS to examine the denaturation of two photosynthesis membrane proteins: CP43 and CP47. THz-TDS was proven to be useful in discriminating the different conformational states of given proteins with similar structure and in monitoring the denaturation process of proteins.

Rapid purification of photosystem I chlorophyll-binding proteins by differential centrifugation and vertical rotor.

Photosystem I (PSI), which consists of a core complex and light-harvesting complex I (LHCI), is an important multisubunit pigment-protein complex located in the photosynthetic membranes of cyanobacteria, algae and plants. In the present study, we described a rapid method for isolation and purification of PSI and its subfractions. For purification of PSI, crude PSI was first prepared by differential centrifugation, which was applicable on a large scale at low cost.